Rectifier



C. A. ESCOFFERY ETAL RECTIFIER Filed July 22, 1947 facer/fin' INVENTORSC14/AEZ E6 f 1-..-! .u t: N

Patented Dec. 28, i948 assure kaernten Charles A. Escoery and Walter H.Blank, East Orange, N. J., asslgnors to Federal Telephone and RadioCorporation, New York, N. Y., a corporation of Delaware Application July22, v1947, Serial No. 762,696

Claims. l

Our invention relates to rectiers and is particularly directed tostructural improvements in the dry-plate rectifiers of thesenil-conductor type.

The semi-conductor type rectifier contemplated here comprises a baseplate with a coating of semi-conducting material such as selenium. Thecoated material is overlaid with a counterelectrode, such asa lowmelting alloyoi cadmium, tin, bismuth and lead, terminals beingelectrically connected to the base plate and to the counterelectrode.The coated materials are thin and are easily damaged mechanically, andare easily corroded in certain atmospheres.

An object oi our invention is to provide an irnproved dry-plate rectierof the semi-conductor type.

Another object of our invention is to provide e. semi-conductorrectifier that is compact, selfcontained, and that protects the coatedmaterials from mechanical as well .as chemical damage.

The scope of our invention is defined in the appended claims andembodiments of our 'lnvention are described in the followingspecification and shown inthe accompanying drawings, in which:

Figs. 1, 3, and 5 are longitudinal sectional views of three embodiments;and

Figs. 2 and 4 are sectional detail of alternative terminals. f

Our rectifier comprises a metal tube or cylinder i of any desiredcross-sectional shape, a round cross-section being shown. On theinterior wall of the tube is applied a layer of semi-conducting material2 such as selenium, and on the selenium layer is applied a thin coating3 of counterelectrode alloy. Unidirectional current carryingcharacteristics are found to exist between terminals connected to themetal tube and to the counter-electrode so that the assembly may beemployed for reati-lying alternating current.

The electrical terminals maycomprise metal caps i and 5, as shown inFig. 1, fitted over the ends o1" the tube, one cap Il being mounteddirectly on and electrically connected to the tube and the other cap 5,being insulatingly carried on the tube and electrically connected tothecounterelectrode. The cap i is telescoped over the tube and brazed orsoldered directly to the tube to hermetically seal the end of the tube,care being taken to maintain electrical separation between the cap andthe end of the counter-electrode. An insulating washer or disc 6 may beinserted be tween the end of the tube and the cap.

The opposite end of the tube is likewise sealed,

but here, the cap is electrically insulated from the tube by a layer ofinsulation applied around and across the end of the tube, or if desired,by a sleeve 'l and a washer d of insulating fiber tted inside Ythe cap.The edge of the cap is hermetically sealed to the side of the tube withan adherent ller 9 of insulating plastic material. To electricallyconnect the cap to the counterelectrode, a metal spring clip lil itattached to the center of the cap to extend into the end of the tube andyieldingly bear against the counterelectrode. The spring clip may bespot welded to the cap or threaded through hoies in the cap and solderedas shown.

, The semi-conducting layer 2 and the thin counter-electrode nlm il arecompletely enclosed and protected from mechanical damage and are sealedfrom injurious atmospheres. The finished rectifier is similar inappearance to a cartridge type fuse and may conveniently be mounted in afuse-type holder for easy replacement.

Terminal wires are, if desired, easily connected, mechanically andelectrically, to our novel rectifier. As shown in Fig. 2, thecounter-electrode connection is made through the metal spring clip illattached to a lead-in conductor il extending through the center of apreformed cap i2 of insulating material. The cap is preferably securedin place with an adhesive that will effect a good seal, and the hole forthe conductor may be closed with a patch of plastic i3. i i

In Fig. 3, the terminal conductors lli and it extend centrally fromopposite ends of the tube. and a structure provided that is mechanicallystrong and pleasing in appearance. The conductor id is welded orsoldered to the side of the tube and is then cast or molded in aninsulating thermoplastic cap le of any desired configuration. Theconnection of conductor l5 to the inside counter-electrode is made by asolid rod or plug Il of conductive material, such as copper or hardcarbon. For a snug iit, the plug and the opening at the end of the tubeshould be tapered. A molding of plastic i3 seals and forms the end ofthe rectifier around the plug, and the conductor l5 is soldered to theend of the plug.

Another capping arrangement is shown in Fig. 4 whereby conduction fromthe counterelectrode layer is obtained by extending the selenium andcounter-electrode layers over the end of the tubular member as indicatedat I9 and 20. The cap 2l is thenv hermetically sealed to the tube withinsulating plastic 22..

The cylinder or tube i has thus far been con sidered as of mtal, but itis apparent a tube of insulating material may be substituted. In Fig. wesho a tube 23 either of glass or hard thermoplastic w ich is metalizedat 26 to forma base for the selenium and counter-electrode layers 25 andshown.

To internally coat the tube with metals, electroplating is preferred,although electrostatic deposition may be employed. or dipping orspraying with the proper solutions of the metals may be used.

The entire outer surface of the tube is eiective in cooling the rectierin operation, and since the outside surface area is proportionallylarger than the area of the rectifying materials, the operatingtemperature of the rectifying materials is lower, for a given currentbetween terminals, than dry-plate rectlilers of other shapes.

Our novel rectifier is self protected, is compact and mechanicallystrong, is attractive, and is hermetically sealed to preventdeterioration or corrosion of the selenium or counter-electrode layers.

We claim:

1. A rectier comprising a tubular member, at least the interior surfaceportion being electrically conductive material, a semi-conductivematerial coated on the said electrically conductive portion of saidmember, a counter-electrode layer on sai'd semi-conductive material, andcaps sealing the ends of said member, said caps including meanselectrically connected, respectively. to said member and to saidcounter-electrode.

2. A rectier according to claim 1 wherein said member includes a tube ofinsulating material and the electrically conductive surface portion is alayer of conductive material coating the interior surface of the tube.

3. A rectiiier according to claim 2 wherein said layer of conductivematerial extends outwardly over both ends of said tube and s'aidsemi-conductive material and said counter-electrode layer extendoutwardly of one end of said tube.

4. A rectier comprising a tube, a semi-conducting iayer on the interiorwall of said tube, and counter-electrode material on said layer, and acap over one end of said tube, said cap including therewith a conductiveelement disposed in said tube in conductive relation with saidcounterelectrode material.

5. A rectier comprising a tube. material having electrical rectifyingproperties on the interior .of said tube, a conductor connected to thewall of said tube, and a cap of insulating material for the end of saidtube, said cap inclosing a portion of said conductor.

6. A rectifier comprising a hollow cylinder. semi-conducting andcounter-electrode material on the interior wall surface of saidcylinder; and a plug of conducting material extending into said cylinderand contacting the ccunterelectrodema terial.

trically containing only said rectifying material.

9. A rectifier according to claim 8, wherein the second mentionedclosure comprising a metal cup, said cup being iltted over the end ofsaid tube, with a sleeve of insulating material between the walls ofsaid cup and tube.

10. A rectifier according to claim 8, wherein the rectifying materialextends over one end of said tube for direct contact by the metalclosure.

CHARLES A. ESCOFFERY.

WALTER H. HAWK.

No references cited.

